Liquid dielectric

About: Liquid dielectric is a research topic. Over the lifetime, 3702 publications have been published within this topic receiving 45150 citations.

Dielectric breakdown of polymeric insulation films under AC, DC and pulsed voltages

Abstract: Polymeric insulation materials are widely used in power generation and energy storage apparatuses. Several examples are: dielectric films for capacitors and resistors; encapsulations for electronic components and devices; insulations for power cables and electrical machines. The dielectric breakdown behaviors of these insulation materials are dependent of electrical stress conditions, chemical structures and their application environment, such as temperature. In this paper, the electrical stress and chemical structure effects on breakdown strength of some typical insulation films are presented and discussed.

Implications from the influence of electrohydrodynamic motion on breakdown with respect to the discharge mechanism in dielectric liquids

Abstract: Electrical discharge measurements with constant voltage pulses in a thin dielectric liquid layer between plane-parallel electrodes provide information about the dielectric strength as a statistical distribution of the time lags to breakdown. Under a large variety of circumstances, the time-lag distributions are composed of two main parts, termed the fast and the normal components. The nature of these components has been identified. The initial fast component lasts as long as the electrical charges, present or created in the liquid, have not yet been able to induce electrohydrodynamic motion. When the point of instability is reached, the probability of breakdown drops by a large amount as evidenced by the normal component of the time-lag distribution. The ions in the liquid, which are responsible for the electrohydrodynamic instability, also condition the electric-field distribution. The peak value of the local field strength is likely to determine the breakdown characteristics. >

Experimental investigation into three-dimensional wavy liquid films under the influence of electrostatic forces

Abstract: Three-dimensional interfacial waves that develop on the free surface of falling liquid films are known to intensify heat and mass transfer. In this context, the present paper studies the effect of electrostatic forces applied to a falling film of dielectric liquid on its three-dimensional nonlinear wave dynamics. Therefore, measurements of the local film thickness using a confocal chromatic imaging method were taken, and the complex wave topology was characterized through photography. The experiments show a complex interaction between the electric field and the hydrodynamics of the falling film, whereby electrostatic forces were found to both increase and decrease wave peak height in different regions of the wave. Additionally, an electrically induced breakup of the three-dimensional wave fronts, which leads to a locally doubled frequency in streamwise direction, is found. The ability to influence the wave topology demonstrated here opens the possibility to optimize heat transfer processes in falling liquid films.

Effect of tangential electric field on the evolution of the Rayleigh-Taylor instability of a dielectric liquid film

Abstract: The effect of surface ponderomotive forces produced by a uniform tangential electric field on the evolution of the Rayleigh-Taylor instability of an isothermal film of a homogeneous incompressible dielectric liquid coating the lower surface of a horizontal insulating plate is studied in the long-wavelength approximation for the hydrodynamic equations and a simplified system of electrostatics equations. The lower boundary of the liquid is the interface with a stationary gas. It is shown in the framework of the linear theory that during the disruption of the continuous film, ponderomotive forces induce the formation of liquid billows extended along the applied field lines.